1. The Field of the Invention
This invention relates to oil and gas drilling, and more particularly to apparatus and methods for reliably transmitting information between downhole drilling components.
2. The Relevant Art
The need for signal repeaters to counteract signal loss encountered when transmitting data from downhole components to the earth's surface is known or has been suggested. Nevertheless, in downhole telemetry systems transmitting data on wires or cables integrated directly into the drill string, few if any useable implementations are known for repeating and amplifying data signals. The following references teach repeaters that are used in wireless electromagnetic or acoustic wave transmission systems, and are not applicable to wired solutions. Furthermore, none of the references address all of the challenges, such as cable routing from the repeater up and down the drill string, that are inherent in wired solutions.
U.S. Pat. No. 6,218,959 issued Apr. 17, 2001 to Smith describes a system and method of fail-safe communication of information transmitted in the form of electromagnetic wave fronts that propagate through the earth between surface equipment and downhole components. The system comprises two or more repeaters disposed within a well bore such that the two repeaters receive each signal carrying the telemetered information. The repeater that is farther from the source includes a memory device that stores information carried in the signal. A timer device, in the repeater that is farther from the source, triggers the retransmission of the information after a predetermined time period, unless the repeater that is farther from the source has detected a signal carrying the information, generated by the repeater, that is closer to the source.
U.S. Pat. No. 6,177,882 issued Jan. 23, 2001 to Ringgenberg et. al teaches downhole repeaters that utilize electromagnetic and acoustic waves to retransmit signals carrying information and methods for use of the same. The repeaters and methods provide for real-time communication between downhole equipment and the surface, and for the telemetering of information and commands from the surface to downhole tools disposed in a well using both electromagnetic and acoustic waves to carry information. The repeaters and methods detect and amplify signals carrying information at various depths in the well bore, thereby alleviating signal attenuation.
U.S. Pat. No. 6,160,492 issued Dec. 12, 2000 to Herman teaches an electromagnetic telemetry system for changing the operational state of a downhole device. The system comprises an electromagnetic transmitter disposed in a first well bore that transmits a command signal. An electromagnetic repeater disposed in a second well bore receives the command signal and retransmits the command signal to an electromagnetic receiver disposed in a third well bore that is remote from the first well bore. The electromagnetic receiver is operably connected to the downhole device such that the command signal received from the electromagnetic repeater is used to prompt the downhole device to change operational states.
U.S. Pat. No. 6,144,316 issued Nov. 7, 2000 to Skinner teaches an electromagnetic and acoustic signal repeater for communicating information between surface equipment and downhole equipment. The repeater comprises an electromagnetic receiver and an acoustic receiver for respectively receiving and transforming electromagnetic input signals and acoustic input signals into electrical signals that are processed and amplified by an electronics package. The electronics package generates an electrical output signal that is forwarded to an electromagnetic transmitter and an acoustic transmitter for generating an electromagnetic output signal that is radiated into the earth and an acoustic output signal that is acoustically transmitted.
U.S. Pat. No. 6,075,461 issued Jun. 13, 2000 to Smith teaches an apparatus, method and system for communicating information between downhole equipment and surface equipment. An electromagnetic signal repeater apparatus comprises a housing that is securably mountable to the exterior of a pipe string disposed in a well bore. The housing includes first and second housing subassemblies. The first housing subassembly is electrically isolated from the second housing subassembly by a gap subassembly having a length that is at least two times the diameter of the housing. The first housing subassembly is electrically isolated from the pipe string and is secured thereto with a nonconductive strap. The second housing subassembly is electrically coupled with the pipe string and is secured thereto with a conductive strap. An electronics package and a battery are disposed within the housing. The electronics package receives, processes, and retransmits the information being communicated between the downhole equipment and the surface equipment via electromagnetic waves.
In view of the foregoing, what are needed are apparatus and methods providing signal amplification in high-speed downhole telemetry systems that transmit data using cables or wires directly integrated into the drill string.
What are further needed are apparatus and methods to seal electronics of the repeater from the surrounding environment, while providing routing of cables to and from the repeater traveling uphole and downhole.
It would be a further advance to provide apparatus and methods that not only repeat or amplify a signal, but could also gather data from various sensors such as inclinometers, pressure transducers, thermocouplers, accelerometers, imaging devices, seismic devices, and the like, as well as provide control signals to various of these device to control them remotely.